CBSE Class 12 Biology 2025 question paper (57/6)

1. A.
   DNA world
2. B.
   RNA world
3. C.
   Protein world
4. D.
   Lipid world

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1. A.
   Inducible regulation
2. B.
   Repressible regulation
3. C.
   Negative regulation
4. D.
   Positive regulation

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1. A.
   Polymorphism in repetitive sequences.
2. B.
   Single-base DNA differences.
3. C.
   Single changes in nucleotide of mRNA.
4. D.
   Loss or gain of a gene function.

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1. A.
   $0{\cdot}16$
2. B.
   $0{\cdot}36$
3. C.
   $0{\cdot}24$
4. D.
   $0{\cdot}48$

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1. A.
   (i), (ii) and (iv)
2. B.
   (ii), (iii) and (v)
3. C.
   (ii), (iv) and (v)
4. D.
   (i), (iii) and (iv)

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1. A.
   Dominant X-linked
2. B.
   Autosomal dominant
3. C.
   Recessive X-linked
4. D.
   Autosomal recessive

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1. A.
   (i) and (ii)
2. B.
   (ii) and (iii)
3. C.
   (iii) and (iv)
4. D.
   (i) and (iv)

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1. A.
   Genes on non-homologous chromosomes and absence of linkage
2. B.
   Two or more genes on homologous chromosomes
3. C.
   Linked genes located on the same chromosomes
4. D.
   Two or more distant genes present on the same chromosome

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1. A.
   Metamorphosis
2. B.
   Metastasis
3. C.
   Metabolism
4. D.
   Metagenesis

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1. A.
   EcoR I
2. B.
   Pvu II
3. C.
   Sal I
4. D.
   Pst I

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1. A.
   Lipases and pectinases
2. B.
   Pectinases and proteases
3. C.
   Proteases and cellulases
4. D.
   Nucleases and lipases

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1. A.
   Insect-eating finches
2. B.
   Seed-eating finches
3. C.
   Cactus-eating finches
4. D.
   Fruit-eating finches

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Greater the evolutionary distance, greater are the differences in the nitrogenous bases.
2. B.
   Lesser the evolutionary distance, greater are the differences in the nitrogenous bases.
3. C.
   Greater the evolutionary distance, lesser are the differences in the nitrogenous bases.
4. D.
   Lesser the evolutionary distance, lesser are the differences in the nitrogenous bases.

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1. A.
   28S rRNA
2. B.
   $5{\cdot}8$S rRNA
3. C.
   26S rRNA
4. D.
   23S rRNA

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1. A.
   9
2. B.
   3
3. C.
   4
4. D.
   1

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1. A.
   Identify approximately 20,000 – 30,000 genes in human DNA.
2. B.
   Determine the sequence of two billion chemical base pairs of human DNA.
3. C.
   Trace human history and disease associated sequences.
4. D.
   Address the ethical, legal and social issues that may arise from the project.

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1. A.
   Autosomal recessive trait
2. B.
   X-linked dominant trait
3. C.
   X-linked recessive trait
4. D.
   Autosomal dominant trait

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1. A.
   (i), (ii) and (iv)
2. B.
   (ii), (iii) and (v)
3. C.
   (ii), (iv) and (v)
4. D.
   (i), (iii) and (iv)

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1. A.
   $0{\cdot}21$
2. B.
   $0{\cdot}42$
3. C.
   $0{\cdot}48$
4. D.
   $0{\cdot}56$

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1. A.
   20%
2. B.
   40%
3. C.
   30%
4. D.
   60%

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1. A.
   (i) and (ii)
2. B.
   (ii) and (iii)
3. C.
   (iii) and (iv)
4. D.
   (i) and (iv)

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1. A.
   Adenovirus
2. B.
   Retrovirus
3. C.
   Rhinovirus
4. D.
   Nucleopolyhedrovirus

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1. A.
   Archaeopteryx
2. B.
   Salamander
3. C.
   Coelacanth
4. D.
   Lobefins

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1. A.
   Pvu II
2. B.
   Pst I
3. C.
   EcoR I
4. D.
   BamH I

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1. A.
   $\text{CH}_3$, $\text{CO}_2$, $\text{H}_2$
2. B.
   $\text{H}_2$, $\text{NH}_3$, $\text{CH}_4$
3. C.
   $\text{H}_2\text{O}$, $\text{Cl}_2$, $\text{H}_2\text{S}$
4. D.
   $\text{O}_2$, $\text{CH}_3$, $\text{H}_2$

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Greater the evolutionary distance, greater are the differences in the nitrogenous bases.
2. B.
   Lesser the evolutionary distance, greater are the differences in the nitrogenous bases.
3. C.
   Greater the evolutionary distance, lesser are the differences in the nitrogenous bases.
4. D.
   Lesser the evolutionary distance, lesser are the differences in the nitrogenous bases.

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1. A.
   Polypeptide only
2. B.
   mRNA only
3. C.
   Polypeptide, tRNA and rRNA
4. D.
   mRNA, tRNA and rRNA

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1. A.
   Autosomal dominant
2. B.
   Autosomal recessive
3. C.
   X-linked dominant
4. D.
   X-linked recessive

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1. A.
   $0{\cdot}8$
2. B.
   $0{\cdot}16$
3. C.
   $0{\cdot}32$
4. D.
   $0{\cdot}64$

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1. A.
   (i) and (ii)
2. B.
   (ii) and (iii)
3. C.
   (iii) and (iv)
4. D.
   (i) and (iv)

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1. A.
   (i), (ii) and (iv)
2. B.
   (ii), (iii) and (v)
3. C.
   (ii), (iv) and (v)
4. D.
   (i), (iii) and (iv)

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1. A.
   X-chromosome of father
2. B.
   Y-chromosome of father
3. C.
   One X-chromosome of mother
4. D.
   Both the X-chromosomes of the mother

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1. A.
   CAUCGAAU
2. B.
   UAAGCUAC
3. C.
   AUUCGAUG
4. D.
   GUAGCUUA

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1. A.
   5' end (after start codon) and 3' end (after stop codon).
2. B.
   5' end (before start codon) and 3' end (before stop codon).
3. C.
   5' end (after start codon) and 3' end (before stop codon).
4. D.
   5' end (before start codon) and 3' end (after stop codon).

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1. A.
   GEAC
2. B.
   MALT
3. C.
   NACO
4. D.
   RCH

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1. A.
   Ichthyosaurus
2. B.
   Tyrannosaurus
3. C.
   Stegosaurus
4. D.
   Brachiosaurus

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1. A.
   Nucleopolyhedrovirus
2. B.
   Adenovirus
3. C.
   Tobacco Mosaic Virus
4. D.
   Rhinovirus

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1. A.
   BamH I
2. B.
   EcoR I
3. C.
   Pst I
4. D.
   Sal I

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Greater the evolutionary distance, greater are the differences in the nitrogenous bases.
2. B.
   Lesser the evolutionary distance, greater are the differences in the nitrogenous bases.
3. C.
   Greater the evolutionary distance, lesser are the differences in the nitrogenous bases.
4. D.
   Lesser the evolutionary distance, lesser are the differences in the nitrogenous bases.

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